Interlock system for darkrooms and film storage bins

ABSTRACT

The interlock system interlocks an x-ray darkroom&#39;&#39;s entrance doors, white light system and x-ray film storage bin drawers so that (1) when a bin drawer is open, the entrance doors cannot be opened and the lights cannot be turned on, and so that (2) when either a door is open or a light is on, the bin drawers cannot be opened.

United States Patent Korb [4 1 Aug. 22, 1972 [54] INTERLOCK SYSTEM FOR 3,263,100 7/ 1966 Stephens et al ..307/1 16 DARKROOMS AND FILM STORAGE 3,246,178 4/1966 Comstock, Jr. et a1. 307/142X BINS [72] Inventor: AlbertN Korb, 549 N- Janett St. 2,922,084 1/1960 Framz ..317/136 X Portland Oreg' 97217 Primary Examiner-J. D. Miller 22] Filed: June 14, 1971 Assistant Examiner-Harry E. Moose, Jr. pp No 152 822 Attorney-Buckhom, Blore, Klarquist and Sparkman [57] ABSTRACT 307,149 317/ The interlock system interlocks an x-ray darkrooms I c c u a u a n I u I I u s o u I I n I I I a u n a n.- Q 0 I u u c I n c I i [58] Field of fig 2 storage bin drawers so that (1) when a bin drawer is open, the entrance doors cannot be opened and the lights cannot be turned on, and so that (2) when .[56] References cued either a door is open or a light is on, the bin drawers UNITED STATES PATENTS cannot be Opened 3,308,714 3/ 1967 Friedel ..95/90 X 13 Claims, 2 Drawing Figures '0 (LT. SWITCH) g 14 R 11 w -("T' Mom 32 LIGHT CIRCUIT IISV. AC

6L I i 46 BIN S 2 DOOR LATCH 7 CIRCUIT 4; n- 2:65? 34b- I iffic i4 15 a ic Patented Aug. 22, 1972 IO l2 (LT. SWIT CH) R (LI N. OFF) H5V. AC

FIG.

LIGHT CIRCUIT FIGv 2 SBJVIIYTCHES 22a g h TCH (BINS NC.) 28 6L8 25 I BIN LATCH 42 CIRCUIT S V J EHES '1 O (DOORSNC) Ej- BUCKHORN, BLORE, KLARQ FROM DOOR

ALBERT N. KORB INVENTOR UIST & SPARKMAN ATTORNEYS INTERLOCK SYSTEM FOR DARKROOMS AND FILM STORAGE BINS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a locking system for preventing exposure of x-ray film in film storage bin drawers commonly found in darkrooms.

2. Description of the Prior Art Hospitals, medical clinics and other places which use and develop x-ray film have darkrooms where such film is processed. The unexposed x-ray film is commonly stored in x-ray film bin drawers in the darkroom. When full,.a single x-ray film bin usually contains several hundred dollars worth of unexposed x-ray film which can become exposed and therefore rendered useless if by accident, neglect or ignorance the film bin is left open to any source of white light. This can easily happen and does happen on occasions, especially in busy x-ray departments of hospitals and clinics. When it happens, not only is there considerable monetary loss, but an entire x-ray department can be closed down during a very busy and critical period until the film bin is restocked.

When a bin full of film is exposed, there is also the time-consuming process of having a darkroom technician examine every film to determine how much, if any, can be saved. Although the top several films in a stack within the bin may protect the center portions of the lower films in the stack, usually the top edge and at least one side edge of every film in the stack will be exposed for a distance of from one-half inch to 2 or 3 inches in from the edge, leaving a black edge which can cut out important details such as a patients name or an important feature of a patient to be-examined or diagnosed.

Others have attempted to solve the problem by educating darkroom technicians and other personnel. However, in a busy or emergency situation, this education is often forgotten, especially among newer personnel.

Another device is available that will automatically turnoff the white lights of a darkroom when a film bin drawer is opened. However, such prior system does not prevent the exposure of film in an open bin when a darkroom door is opened to admit white light from outside the darkroom, nor does it prevent opening of the bin drawer when a white light is on.

Accordingly, there is a need for a fail-safe system for preventing the unintentional exposure of film in a storage bin to harmful light.

I SUMMARY OF THE INVENTION In accordance with the invention, an interlock system is provided which interlocks the film bin drawers in a darkroom with the darkroom doors and white lights of the room in a manner so that (1) when a darkroom white light is on, the bin drawer is locked the bin drawer, electrically operated bin locks operated by opening and closing the darkroom doors or the darkroom white light switches, and a bin-operated switch in the white light circuit.

The primary object of the invention is to provide an interlock system for darkrooms which prevents the unintentional exposure of film in a film storage bin to destructive light sources.

Another important object of the invention is to provide such an interlock system which is relatively foolproof in operation.

Another important object is to provide such an interlock system that is simple and economical to manufacture, install and maintain.

Still another object is to provide such an interlock system that will not change, affect or interfere with normal, accepted darkroom procedures and routine.

BRIEF DESCRIPTION OF THE DRAWING The foregoing and other objects, features and advantages of the invention will become more apparent from the following detailed description which proceeds with reference to the accompanying drawing, wherein:

FIG. 1 is a circuit diagram showing a typical electrical interlock system in accordance with the invention; and

FIG. 2 is a schematic view of a control panel housing key elements of the system.

DETAILED DESCRIPTION With reference to the drawing, the electrical diagram of FIG. 1 illustrates one form of electrical wiring for the invention. Leads L-l, 1.!2 and L-3 at the top of the diagram represent the standard three-wire building leads in a conventional l l5-volt A.C. circuit.

A line 10 in the building circuit represents the white light circuit of an x-ray darkroom and includes a conventional on-off light switch 12, fuse 14, and one or more white lights 16. A relay 18 is wired in the light circuit in parallel with the white light sources 16 but in se-' ries with light switch 12.

A transformer 20 converts the 1l5-volt AC. to 24- volt A.C. for the remainder of the electrical interlock system.

In the 24-volt lines, there is a door latch circuit represented by line 22. Two bin switches 24, 25 are connected in parallel in this circuit, assuming there are two bin drawers. These switches control the operation of a pair of electrically operated door-locking means, including a door latch 26 in line 22 and a second door latch 28 in parallel with door latch 26 in line 22a, assuming there are two doors to the darkroom. A second relay 30 is connected in parallel with the door latches in line 22b but in series with the bin switches 24, 25.

Bin switches 24, 25 are normally open when the bins are closed, thereby rendering the door latches 26, 28 inactive so that the darkroom doors can be opened and closed so long as both bins remain closed.

Relay 30 includes a normally closed relay contact 32 in the light circuit 10. Thus when a bin is opened to close either bin switch 24, 25, relay 30 is energized to open its relay contact 32, thereby breaking the light circuit to turn off any white lights that may be on. However, relay contact 32 is in parallel with relay 18 so that relay 18 can still be controlled by opening and closing light switch 12.

The system includes a third bin latch circuit represented by line 34. Assuming there are two film bins in the room, a pair of electrically operated binlocking means are connected in this circuit. These locking means include a bin latch 36 in line 34 and a second bin latch 38 connected in parallel with bin latch 36 in line 34a.

A normally open relay contact 40 operated by relay 18 is connected in the bin latch line 34 in series with both bin latches. A pair of door switches 42, 44, one for each door, are also provided in the bin latch circuit and connected in parallel with the relay contact 40 and with each other but in series with both bin latches in lines 34b, 340. The door switches are normally open when their respective doors are closed.

If desired, panic buttons 46, 48 may be provided outside the two doors for enabling a person outside the darkroom to enter in the event of an emergency, such as a disabled person in the darkroom with a bin drawer open. These panic buttons are shown connected in series, respectively, with door latches 26, 28 in lines 22, 22a.

Many different types of electrically operated locking means can be used for the door latches and the bin latches. In a typical form of the invention, the bin and door latches are electrically operated dead bolt latches. The door and bin switches can be, for example, microswitches, a suitable one of which is manufactured by Robertshaw Controls Company under designation 1CMD12AXX-A22.

The components of the interlock system, except for the door and bin latches and door and bin locks, may be provided at a single control panel 50 shown in FIG. 2. This panel includes a five-wire connector cable 52 with a plug 53 for connection to a wall socket outlet. The panel houses both relays 18 and 30, as well as transformer and a 12-point terminal block shown at 54 located on the outside of the control panel. Lead cables 56, 57 extend from the various doors and bins to the terminal block.

OPERATION With the circuit as described, the interlock system operates as follows: With light switch 12 open as shown, the white light source 16 is off and relay 18 is de-energized. Thus relay contact 40 in the bin latch circuit remains open so that bin latches 36 and 38 are deenergized. Under these conditions the bin drawers can be freely opened so long as the doors of the darkroom remain closed so that door switches 42 and 44 remain open.

When light switch 12 closes to turn on white light 16, relay 18 is energized. Relay 18 closes relay contact 40, completing the bin latch circuit to operate bin latches 36, 38 so as to lock both film bin drawers. So long as light switch 12 remains closed, the bin drawers remain locked and cannot be opened to expose film. However, by reopening light switch 12 to turn off light 16 and deenergize relay 18, the bin locks retract to permit the bin drawers to be opened.

Referring now to the door latch circuit, and assuming bin drawers can be freely opened. When either bin drawer is opened, it closes its respective bin switch 24 or 25, operating both door latches 26, 28 so as to lock the entrance doors to the darkroom. At the same time the closed bin switch energizes relay 30, opening relay contact 32 in the light circuit, thereby ensuring that the light 16 cannot be turned on regardless of position of light switch 12 so long as the open bin drawer remains open. Of course, in the unlikely event that a darkroom technician should faint while inside the darkroom with a bin drawer open, someone outside the darkroom can gain emergency access by pressing one of panic buttons 46 or 48 to release a door latch. As described, the bin switches in the door lock circuit serve as an effective door lock-operating means and light de-energizing means.

Turning to the bin latch circuit 34, it has already been mentioned that with light switch 12 closed, relay l8 closes relay contact 40 to operate bin latches 36, 38 so as to lock the bins. The normally open door switches have the same efiect. That is, door switches 42 and 44 remain open so long as the darkroom doors remain closed. However, as soon as one of the darkroom doors opens, its corresponding switch 42 or 44 closes to operate the bin latches 36, 38 so as to lock the bin drawers closed. Thus the door switches operate independently of relay contact 40, relay l8 and light switch 12 to ensure that white light sources from outside the darkroom will not expose film in an open film bin within the darkroom, even though the white lights in the darkroom may be turned off. As described, the door switches function as bin lock-operating means as do also the light switch 12, relay l8 and relay contact 40 taken together. Either closing the light switch or opening a door operates the bin locks to lock the bins. However, the reverse is not true. In this regard, both the doors must be closed and the light switch must be open to release the bin locks so that the bins can be opened.

An important feature of the described electrical interlock system is that it will not interfere with or change darkroom routine unless and until accepted procedures are not followed; that is, unless a bin drawer is left open, a light is left on, or a door is left open.

Another feature is that a power failure will have a minimal effect on the system. In such event, the door and bin locks release so persons within the darkroom can get out, but the light circuits are broken. Yet if a bin is left open, the absence of light within the room should save the film.

From the foregoing description, no doubt other possible electrical circuits to accomplish the same results will occur to those skilled in the art. For example, relay 30 could be wired in a circuit separate from the door latch circuit and operated through the second throw of a double-throw bin switch rather than being connected in parallel with the door latches as shown. Relay 18 could also be controlled by a double-throw light switch in place of the single throw switch 12 shown, in a similar manner.

Having illustrated and described what is presently a preferred form of the invention, it should be apparent to those skilled in the art that the same pennits of modification in arrangement and in detail. I claim as my invention all such modifications as come within the true spirit and scope of the following claims.

I claim:

1. An interlock system for preventing accidental exposure of film in a film storage bin drawer within a darkroom having an entrance door and a light source,

bin-locking means,

door-locking means,

on-ofi' light switch means in a light circuit for said light source,

and interlock means operably interlocking said bin,

door and light source in a manner such that: (1)

said switch means when closed to energize said light source activates said bin-locking means to lock said bin, and (2) said film bin when open activates said door-locking means to lock said door and opens said light circuit, and (3) said door when open activates said bin-locking means to lock said bin, whereby said bin cannot be opened when said door is open or when said light is on and said door cannot be opened and said light cannot be turned on when said bin is open.

2. A system according to claim 1 wherein said interlock means includes:

first means responsive to the closing of said light circuit for operating said bin-locking means in a manner to lock said bin,

second means responsive to the opening of said door for operating said bin-locking means in a manner to lock said bin,

said first and second means being operably interrelated in a manner so that said bin-locking means operates to lock said bin if either said light circuit is closed or said door is open and operates to unlock said bin only if both said door is closed and said light circuit is open.

3. A system according to claim 2 including:

third means responsive to the opening of said bin for operating said door-locking means in a manner to lock said door and for opening said light circuit independently of the position of said light switch means.

4. A system according to claim 2 wherein said binlocking means is electrically operated and said first means includes an electrical bin lock circuit for energizing said bin-locking means, an electrical relay means energized when said light switch means is closed, and a normally open relay contact in said bin lock circuit which is closed when said relay means is energized.

5. A system according to claim 4 wherein said second means comprises a door-operated electrical switch means connected in parallel with said relay contact in said bin lock circuit.

6. A system according to claim 3 wherein:

said bin-locking means and said door-locking means are electrically operated,

said first means includes an electrical bin lock circuit for energizing said bin-locking means, anelectrical relay means energized when said light switch means is closed, and a normally open relay contact in said bin lock circuit which is closed when said relay means is energized,

said second means includes a door-operated electrical switch means connected in parallel with said relay contact in said bin lock circuit, and said third means includes an electrical door lock circuit, a bin-operated electrical switch means in said door lock circuit, a second electrical relay said first and second bin lock-operating means being I operable independently of one another in a manner so that operation of either one of said lock-operating means operates said locking means to lock said bin,

said first and second bin-locking means being cooperatively interrelated in a manner so that operation of both said lock-operating means is required to operate said locking means to unlock said bin,

the operation of said first bin lock-operating means being controlled by said light-energizing means in a manner so that said bin is locked when said light source is energized, the operation of said second bin lock-operating means being controlled by said door in a manner so that said bin is locked when said door is open,

whereby when either said light source is energized or said door is open said bin is locked, and only when both said light source is de-energized and said door is closed said bin is unlocked.

8. A system according to claim 7 wherein said binlocking means is electrically operated and in a bin lock circuit, said light-energizing means includes an on-ofi' light switch in an electrical light circuit for said light source, said first bin lock-operating means includes an electrical relay means in a circuit controlled by said light switch and a relay contact in said bin lock circuit operated by said relay means, and said second bin lockoperating means includes a door-operated electrical switch connected in parallel with said relay contact in said bin lock circuit.

9. An interlock system for preventing accidental exposure of film in a film storage bin wherein said bin includes a bin closure member and is in a darkroom having at least one entrance door and one light source, said system comprising:

door-locking means for locking said door,

light-energizing means for energizing said light source,

and control means operable by opening and closing said bin closure member for controlling the operation of said door-locking means and said lightenergizing means, said control means being operable in a manner so as to de-energize said light source and lock said door when said bin is open and so as to unlock said door and condition said energizing means to energize said light source when said bin is closed. 10. A system according to claim 9 wherein:

said door-locking means is electrically operated,

said light-energizing means includes an electrical light circuit containing said light source, electrical relay means, and a relay contact in said light circuit operated by said relay means,

said control means includes a bin closure-operated electrical switch means controlling the energization of said relay means and said door-locking means.

11. An interlock system for preventing accidental exposure of film in a film storage bin means wherein said bin means includes a bin closure member and is in a darkroom having at least one entrance door, said system comprising:

bin-locking means for locking said bin means,

bin-lock operating means,

said bin-lock operating means including control means on said entrance door normally maintaining said bin means in an unlocked condition when said door is closed and operable to lock said bin means when said door is opened.

12. An interlock system for preventing accidental exposure of film in a film storage bin means wherein said bin means includes a bin closure member and is in a darkroom accessible to a light source damaging to film, said system comprising:

bin-locking means for locking said bin means,

means for illuminating said darkroom with said damaging light source,

bin-lock operating means,

said bin-lock operating means including control means normally maintaining said bin means in an unlocked condition when said light source is not illuminating said darkroom but operable when said darkroom is illuminated by said light source to lock said bin means.

13. An interlock system for preventing accidental ex posure of film in a film storage bin means wherein said bin means includes a closure member and is in a darkroom having at least one entrance door, said system comprising:

door-locking means for locking said entrance door,

door-lock operating means,

said door-lock operating means including control means on said bin means,

said control means being operable when said bin means is closed to maintain said door in an unlocked condition and being operable when said bin means is opened to lock said door closed. 

1. An interlock system for preventing accidental exposure of film in a film storage bin drawer within a darkroom having an entrance door and a light source, bin-locking means, door-locking means, on-off light switch means in a light circuit for said light source, and interlock means operably interlocking said bin, door and light source in a manner such that: (1) said switch means when closed to energize said light source activates said bin-locking means to lock said bin, and (2) said film bin when open activates said door-locking means to lock said door and opens said light circuit, and (3) said door when open activates said bin-locking means to lock said bin, whereby said bin cannot be opened when said door is open or when said light is on and said door cannot be opened and said light cannot be turned on when said bin is open.
 2. A system according to claim 1 wherein said interlock means includes: first means responsive to the closing of said light circuit for operating said bin-locking means in a manner to lock said bin, second means responsive to the opening of said door for operating said bin-locking means in a manner to lock said bin, said first and second means being operably interrelated in a manner so that said bin-locking means operates to lock said bin if either said light circuit is closed or said door is open and operates to unlock said bin only if both said door is closed and said light circuit is open.
 3. A system according to claim 2 including: third means responsive to the opening of said bin for operating said door-locking means in a manner to lock said door and for opening said light circuit independently of the position of said light switch means.
 4. A system according to claim 2 wherein said bin-locking means is electrically operated and said first means includes an electrical bin lock circuit for energizing said bin-locking means, an electrical relay means energized when said light switch means is closed, and a normally open relay contact in said bin lock circuit which is closed when said relay means is energized.
 5. A system according to claim 4 wherein said second means comprises a door-operated electrical switch means connected in parallel with said relay contact in said bin lock circuit.
 6. A system according to claim 3 wherein: said bin-locking means and said door-locking means are electrically operated, said first means includes an electrical bin lock circuit for energizing said bin-locking means, an electrical relay means energized when said light switch means is closed, and a normally open relay contact in said bin lock circuit which is closed when said relay means is energized, said second means includes a door-operated electrical switch means connected in parallel with said relay contact in said bin lock circuit, and said third means includes an electrical door lock circuit, a bin-operated electrical switch means in said door lock circuit, a second electrical relay means controlled by said bin-operated switch means, and a second relay contact in said light circuit controlled by said second relay means.
 7. An interlock system for preventing accidental exposure of film in a film storage bin in a darkroom having at least one entrance door and one light source, said system comprising: light-energizing means for selectively energizing said light source, bin-locking means for locking said bin, first bin lock-operating means for operating said bin-locking means to lock said bin, second bin lock-operating means for operating said bin-locking means to lock said bin, said first and second bin lock-operating means being operable independently of one another in a manner so that operation of either one of said lock-operating means operates said locking means to lock said bin, said first and second bin-locking means being cooperatively interrelated in a manner so that operation of both said lock-operating means is required to operate said locking means to unlock said bin, the operation of said first bin lock-operating means being controlled by said light-energizing means in a manner so that said bin is locked when said light source is energized, the operation of said second bin lock-operating means being controlled by said door in a manner so that said bin is locked when said door is open, whereby when either said light source is energized or said door is open said bin is locked, and only when both said light source is de-energized and said door is closed said bin is unlocked.
 8. A system according to claim 7 wherein said bin-locking means is electrically operated and in a bin lock circuit, said light-energizing means includes an on-off light switch in an electrical light circuit for said light source, said first bin lock-operating means includes an electrical relay means in a circuit controlled by said light switch and a relay contact in said bin lock circuit operated by said relay means, and said second bin lock-operating means includes a door-operated electrical switch connected in parallel with said relay contact in said bin lock circuit.
 9. An interlock system for preventing accidental exposure of film in a film storage bin wherein said bin includes a bin closure member and is in a darkroom having at least one entrance door and one light source, said system comprising: door-locking means for locking said door, light-energizing means for energizing said light source, and control means operable by opening and closing said bin closure member for controlling the operation of said door-locking means and said light-energizing means, said control means being operable in a manner so as to de-energize said light source and lock said door when said bin is open and so as to unlock said door and condition said energizing means to energize said light source when said bin is closed.
 10. A system according to claim 9 wherein: said door-locking means is electrically operated, said light-energizing means includes an electrical light circuit containing said light source, electrical relay means, and a relay contact in said light circuit operated by said relay means, said control means includes a bin closure-operated electrical switch means controlLing the energization of said relay means and said door-locking means.
 11. An interlock system for preventing accidental exposure of film in a film storage bin means wherein said bin means includes a bin closure member and is in a darkroom having at least one entrance door, said system comprising: bin-locking means for locking said bin means, bin-lock operating means, said bin-lock operating means including control means on said entrance door normally maintaining said bin means in an unlocked condition when said door is closed and operable to lock said bin means when said door is opened.
 12. An interlock system for preventing accidental exposure of film in a film storage bin means wherein said bin means includes a bin closure member and is in a darkroom accessible to a light source damaging to film, said system comprising: bin-locking means for locking said bin means, means for illuminating said darkroom with said damaging light source, bin-lock operating means, said bin-lock operating means including control means normally maintaining said bin means in an unlocked condition when said light source is not illuminating said darkroom but operable when said darkroom is illuminated by said light source to lock said bin means.
 13. An interlock system for preventing accidental exposure of film in a film storage bin means wherein said bin means includes a closure member and is in a darkroom having at least one entrance door, said system comprising: door-locking means for locking said entrance door, door-lock operating means, said door-lock operating means including control means on said bin means, said control means being operable when said bin means is closed to maintain said door in an unlocked condition and being operable when said bin means is opened to lock said door closed. 